Methods of patterning small features onto substrates are of great importance in the fabrication of many electronic, magnetic, mechanical, and optical devices as well as devices for biological and chemical analysis. Such methods are used, for example, to define the features and configurations of microcircuits and the structure and operating features of planar optical waveguides and associated optical devices.
Optical lithography is the conventional method of patterning such features. A thin layer of photoresist is applied to the substrate surface and selected portions of the resist are exposed to a pattern of light. The resist is then developed to reveal a desired pattern of exposed substrate for further processing such as etching. A difficulty with this process is that resolution is limited by the wavelength of the light, scattering in the resist and substrate, and the thickness and properties of the resist. As a consequence optical lithography becomes increasingly difficult as desired feature size becomes smaller. Moreover applying, developing and removing resists are relatively slow steps, limiting the speed of throughput.
A more recent approach to patterning small features is nanoimprint lithography wherein a nanofeatured molding surface is imprinted into a resist or resist-like material (polymer) and the imprinted pattern is removed to selectively expose the substrate surface. This process eliminates the limitations on resolution caused by the wavelength of light, but nonetheless has limitations imposed by the use and processing of resists or polymers. Further details concerning nanoimprint lithography are set forth in applicant's U.S. Pat. No. 5,772,905 issued Jun. 30, 1998 and entitled “Nanoimprint Lithography” and U.S. Pat. No. 6,482,742 issued Nov. 19, 2002 and entitled “Fluid Pressure Imprint Lithography”. The '905 and '742 patents are incorporated herein by reference.
The electronics and optical communications industries, as well as companies entering new fields of nanotechnology, continue to seek new methods for the production of microcircuits, optical devices and new nanoscale structures. In particular they seek faster processes for patterning substrates with higher resolution patterns.